1. Field of the Invention
Exemplary aspects of the present invention generally relate to a drive transmission mechanism and an image foaming apparatus including the drive transmission mechanism, and more particularly to a drive transmission mechanism having an uncomplicated configuration and good transmission property and an image forming apparatus including the drive transmission mechanism.
2. Description of the Prior Art
Gears, timing belts, and pulleys are generally used for a drive transmission mechanism that transmits a drive force generated by a motor or the like. In the drive transmission mechanism, each of the gears or the pulleys (hereinafter both referred to as drive transmission members) is fitted onto a shaft supported at both ends by bearings. It is important for accurate transmission of the drive force to prevent the drive transmission member and the shaft from being moved not only in a radial direction but also in a thrust direction. In order to restrict movement of the shaft in the thrust direction, the bearing is typically sandwiched between an enlarged diameter portion at the end of the shaft and the drive transmission member fitted onto the shaft.
In such a configuration, however, the drive transmission member may contact a shield plate fixed to an outer ring of the bearing. Consequently, although the shield plate is stationary, the drive transmission member is rotated together with an inner ring of the bearing. As a result, vibration due to friction between the drive transmission member and the shield plate may cause uneven rotation of the shaft.
To solve the above-described problem, the shaft can be given a portion of enlarged or reduced diameter, with a step thus formed at a boundary between a normal diameter portion of the shaft and the enlarged or reduced diameter portion is pressed against the inner ring of the bearing to restrict movement of the shaft in the thrust direction. However, the drive transmission member needs to be fitted onto the shaft, thereby preventing easy assembly of the drive transmission mechanism.
In another approach, as illustrated in FIG. 1, a drive transmission mechanism 110 includes a drive transmission member 30 which is loosely fitted onto a shaft 20 to facilitate assembly of the drive transmission mechanism 110. Accordingly, reliable transmission of the drive force can be achieved even in a case in which a pin 40 inserted into the shaft 20 and a pin seating formed in the drive transmission member 30 contact each other to loosely fit the drive transmission member 30 onto the shaft 20.
However, with such a configuration it is necessary to fix a position of the drive transmission member 30 in the thrust direction with an E-ring (or C-ring) 70 in order to restrict movement of the drive transmission member 30 in the thrust direction. Therefore, a space into which the E-ring (or C-ring) 70 is inserted must be provided between the drive transmission member 30 and a bearing 10. Consequently, a length of the shaft 20 is increased, thereby possibly causing uneven rotation of the shaft 20.